The present invention, in some embodiments thereof, relates to light field acquisition and, more particularly, but not exclusively, to light field reconstruction using extended depth of field (EDOF).
Light field photography (plenoptic photography) is a relatively new technique in the field of computational imaging which is based on measurement of both the location and angle of the light rays. In comparison to normal photography which measures only the intensity of the light reaching the detector, light field photography measures both the intensity on the detector and the direction it arrives from.
Light field imaging has many benefits in comparison to normal imaging since it measures the entire optical function and allows manipulating it computationally. The post capture manipulation allows changing the focus or viewing angle of the image. Furthermore, depth map of the scene can be calculated out of the light field measurement to generate a color 3D model of the scene.
The main technique for light field acquisition is by using a lenslet array (an array of micro-lenses) which is placed in front of the image sensor. Each lens deflects different angles of light rays to different sensor's pixels. This allows measuring both the light ray's location (the specific lenslet it reaches) and its angle (the specific pixel illuminated).
Another way to acquire light fields is by using an attenuation mask and compressed sensing algorithms. The attenuation mask is placed in front of the sensor. By using knowledge on the light fields' sparsity under a certain representation and the attenuation mask one can use compressed sensing algorithms to reconstruct the light field with high resolution. This approach is perused mainly in academia and research centers.
Extended depth of field (EDOF) is a technique that utilizes chromatic aberrations of the optics to generate an image with an extended depth of field while still using a low f number. This technique was mainly used for mid-level cell phone such as Nokia phones. In optics, chromatic aberration is a type of distortion for which the lens has a different focal plane for each color. This is caused due to lens being made of a material having chromatic dispersion (different index of refraction for each color). In this effect each color is focused in a different plane causing a different point spread function (PSF) for each color. Standard optical systems use different type of glasses to minimize this effect. In comparison to standard optics, EDOF technology utilizes the chromatic aberration. Since each color have a different focal length, the optical arrangement will be focused on different planes for different colors. Standard EDOF algorithms use the data from each color channel to generate one all in focus image. This achieves an optical arrangement with an extended depth of field.